Air includes contaminants such as mold, pollen, dust, pet dander, and other particles that can cause mild to severe allergic reactions. Air purifiers have been used to remove these contaminants from the air in people's homes and businesses and alleviate the symptoms associated with allergies and asthma. Several different processes are used in air purifiers to remove the contaminants from the air. One such process uses an air filter that physically traps particles in the air and that pass over the filter.
Another process more recently developed for use in air purifiers is photocatalytic oxidation. Photocatalytic oxidation is the process of irradiating a semi-conductor photocatalyst using short-wave ultraviolet light, generally having a wavelength of less than 385 nanometers. Irradiating the photocatalyst causes a band gap energy to be exceeded and an electron to be promoted from the valence band to the conductive band resulting in an electron-hole pair (h+ and e−). The h+ and e− can react with organic compounds, and the organic compound is oxidized or reduced. For instance, if a molecule which favors giving up an electron, such as ethanol, methanol, or water, is present on the photocatalyst, then the photo-generated hole (h+) can react with the organic compound to generate an oxidized product. The hole accepts the electron and the molecule becomes an electron poor, high energy intermediate. Similarly, if there is an electron acceptor, such as oxygen or hydrogen peroxide and is present on the photocatalyst, then the photo-generated conductance band electrons (e−) can react with it to generate a reduced product. The electron poor molecule accepts the electron from the conduction band and the molecule becomes an electron rich, high energy intermediate. In a complete photocatalytic oxidation reaction, the final products are CO2 and H2O. While air purifiers are extremely useful for a home or commercial user, air purifiers occupy additional space when used with a space heater.
These and other drawbacks exist with current systems.